Why are there penguins living outdoor in summer?

The OZEANEUM in the northern German port city of Stralsund has a rather satisfying rooftop. Here you can enjoy the refreshing Baltic breeze, see the bright blue summer sky above and enjoy the historic Hanseatic town of Stralsund below.

And in the middle of the rooftop sits a rocky pool. Every now and then, a fluffy brown-and-white head pokes out from one of the artificial nesting caves.

A penguin.

I had to look twice to trust my own eyes. It was late July and the rooftop was baking under direct sunshine that standing there in a T-shirt already made me feel warm enough. Yet these birds, commonly supposed to appear in below-ice temperature only, appeared perfectly comfortable.

Had someone forgotten to tell the penguins that they belong in Antarctica?

No. The introductory board explained clearly that these are Humboldt penguins, one of the few penguin species that naturally inhabit temperate, subtropical, and even tropical regions in the Pacific side of South America.

I had always associated penguins with snow, sea ice and the Antarctic and I personally believe many people did it. But nature, as it often does, had another story to tell.

The Humboldt penguin is native to the coastal region ranging roughly from Peru to central Chile, or between about 5 and 43 degrees south latitude. As the digit shows, some of their colonies even live surprisingly close to the equator.

The species owes its name to the German explorer and naturalist Alexander von Humboldt, who observed these penguins during his famous expedition across Latin America between 1799 and 1804. His reports astonished European scientists of the time. Decades later, German zoologist Franz Julius Ferdinand Meyen formally described the species and named it Spheniscus humboldti in Humboldt's honor.

Adding a sentence. Having traveled several times to Germany, I've noticed that Humboldt's name seems to appear almost everywhere. There is the Humboldt University, the Humboldt Foundation, the Humboldt Forum, even the Humboldt penguin.

Apparently, if something has made a meaningful contribution to science or exploration, there is a fair chance Germans have named it after Humboldt.

Unlike their Antarctic relatives, Humboldt penguins have spent millions of years adapting to a much warmer environment. As a result, their famous "tuxedos" are still covering their bodies, but only in principle.

Antarctic penguins wear dense black feathers across their backs. The dark color efficiently absorbs sunlight, helping them stay warm in freezing conditions. For a penguin living near the tropics, however, such a heavy coat would become a liability.

That's why Humboldt penguins evolved lighter, browner plumage that is noticeably less dense than that of emperor or Adélie penguins. Their feathers are shorter and thinner, and every year they undergo what scientists call a catastrophic molt, replacing nearly all of them within just a few weeks.

And their faces — large patches of bare pink skin surround their eyes and extend toward the base of their bill. These featherless areas are rich in blood vessels and serve as natural cooling systems, allowing excess body heat to escape.

Once you know what they are for, those rosy cheeks become even more adorable.

They have even kept diet. Antarctic penguins resemble little walking barrels as thick layers of fat help conserve heat in water that can remain below freezing. In deep contrast, Humboldt penguins are noticeably slimmer, carrying less insulation and dissipating heat more efficiently.

In one word, if emperor penguins, or the most common penguin faces in videos, are built for surviving polar winters, Humboldt penguins are built for avoiding heat stroke.

Yet even all these adaptations cannot fully explain how a penguin manages to thrive so close to the tropics because the two environments are too strikingly contrast to each other.

The question was also answered by Humboldt. During his South American expedition, Humboldt noticed that coastal waters were unexpectedly cold despite their low latitude. Investigating further, he identified a vast current flowing northward from Antarctic waters along the Pacific coast.

Today it is known as the Humboldt Current, or the Peru Current. As its name shows, it cools both the sea and the air above it, creating a remarkably mild coastal climate near Peru. Sea surface temperatures often remain between 15 and 18 C, far cooler than one would expect at those latitudes.

For Humboldt penguins, the current functions as a giant natural air conditioner that even people in Europe are dreaming of. Whenever the sun becomes too intense, they simply dive into cool seawater.

Even more importantly, the Humboldt current supports one of the richest marine ecosystems on Earth. Cold water rising from the deep carries abundant nutrients to the surface, triggering explosive growth of plankton, which in turn feeds enormous populations of fish, squid and krill.

Krill are often associated with Antarctica, yet thanks to the Humboldt Current, these tiny crustaceans also flourish off the coasts of Peru and Chile, providing another valuable food source for penguins.

That's why Humboldt penguins doubly deserve the name: without the Humboldt current, Humboldt penguins would almost certainly not exist.

Standing on that rooftop in Stralsund, I suddenly realized that the climate here, on Germany's Baltic coast, is remarkably similar to the conditions the penguins experience in parts of South America.

The Baltic Sea moderates temperatures throughout the year, winters are relatively mild, summers are pleasant rather than scorching, while strong sea breezes help keep the rooftop comfortable even in July.

No wonder the penguin enclosure is entirely outdoors. The birds spend their days under open skies, exposed to sunshine, wind and rain much as they would along the Pacific coast.

The experience also challenged another assumption I had long held — that penguins belong almost exclusively to Antarctica. Just on the contrary, several species live far from the polar continent:

Magellanic penguins inhabit Argentina and Chile;

African penguins live along the coasts of South Africa and Namibia, benefiting from the cold Benguela Current;

Galápagos penguins survive almost directly on the equator, where the Humboldt Current and the Cromwell Current combine to cool surrounding waters.

Perhaps even more surprising is what paleontologists now believe about penguin origins. The oldest known penguin fossils, dating back about 62 million years, were discovered not in Antarctica but in what is now New Zealand. Current evidence suggests penguins first evolved in a much warmer world before later spreading southward and gradually adapting to polar conditions.

In other words, Antarctica did not create penguins — Penguins eventually adapted to Antarctica.

A bigger thinking is about the oceans themselves. Invisible to us, enormous currents circulate endlessly around the globe, transporting heat, nutrients and life across thousands of kilometers. A slight change in water temperature can reshape an entire coastline, allowing a bird that most of us associate with icebergs to flourish in subtropical South America — or on the roof of a museum in northern Germany.

Sometimes, standing beside a penguin pool, you end up learning more about the planet than about the penguins themselves. The Earth, a rocky planet with so accurately proper distance to the sun that liquid water can exist on it and breed life for 3.8 billion years, is also in a small and subtle corner of the Universe where the natural forces accidentally make good.

Perhaps that is what Humboldt as a science teacher would have appreciated.

zhangzhouxiang@chinadaily.com.cn